On my MacBook Pro laptop running OS X El Capitan (10.11.6), I've been losing Internet connectivity periodically. Though it appears I still have Wi-Fi connectivity, when I attempt to access websites through a browser I find that I can't access sites at times, though a moment before I had no issues browsing the Web. Firefox will display a "Server not found" message. If I go to a Terminal window and try to ping any IP address, I see "request timeout" messages.
$ ping 188.8.131.52 PING 184.108.40.206 (220.127.116.11): 56 data bytes Request timeout for icmp_seq 0 Request timeout for icmp_seq 1 ^C --- 18.104.22.168 ping statistics --- 3 packets transmitted, 0 packets received, 100.0% packet loss $
If I check the status of the WiFi connection using the airport command, I see that it is very noisy, though the signal stength is good, which I would expect, since the laptop is only a few feet from the wireless router.
$ /System/Library/PrivateFrameworks/Apple80211.framework/Versions/Current/Resources/airport -I agrCtlRSSI: -39 agrExtRSSI: 0 agrCtlNoise: -93 agrExtNoise: 0 state: running op mode: station lastTxRate: 73 maxRate: 72 lastAssocStatus: 0 802.11 auth: open link auth: wpa2-psk BSSID: 94:44:52:4a:43:40 SSID: Rain MCS: 7 channel: 11 $
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